Are effective leaders born or made? Why do you believe so? Use a specific example to back up your opinion.

It has long been debated whether or not a person can be taught to be an effective leader or whether a person was simply endowed at birth with a natural ability to lead. This is sometimes referred to as the nature versus nurture debate, or a discussion of management as an art or a science. What do you think? 

Are effective leaders born or made? Why do you believe so? Use a specific example to back up your opinion.